mGRE vs DMVPN

[Oleg Gnedykh]

Hi All !!!
I have started learning DMVPN and found out that DMVPN is mGRE without IPSec.
But I can't find an independent manual about mGRE without DMVPN.
Can anybody explain difference between mGRE and DMVPN ???
 OR  
give me please link to manual solo mGRE !

Thanks in advance dear All !!!

[Cisco Freak]

mGRE is key ingredient to build the DMVPN tunnel. Without mGRE we can't build the DMVPN tunnel.

DMVPN uses a combination of the following technologies to build the tunnel :

1. Multipoint GRE (mGRE) 
2. Next-Hop Resolution Protocol (NHRP) 
3. Dynamic Routing Protocol (EIGRP, RIP, OSPF, BGP) 
4. Dynamic IPsec encryption(Optional)

http://ccieat2016.blogspot.in/2014/12/dmvpn.html

[Oleg Gnedykh]

Hi Freak !!!
Can you looking up to my answer for Jon Marshall

[Jon Marshall]

DMVPN can be run without IPSEC but more often than not it includes IPSEC.

It also includes other technologies one of which is mGRE which is basically the ability to terminate multiple tunnels on a single interface.

Without mGRE every single site, including the hub would need a tunnel per connection to any other site which is not very scalable with a large number of sites.

See this link which explains all the technologies that are part of DMVPN, including mGRE and how they work together -

http://blog.ine.com/2008/08/02/dmvpn-explained/

Jon

[Oleg Gnedykh]

Hi Jon !!!

Thank you for your answer !

I have mentioned about mGRE cause I have saw in Cisco Blue Print R&S Labs a chapter 3.1

"3.1.c [ii] Dynamic GRE" and I have thought it same mGRE. Is it true ? 

[Cisco Freak]

3.1.c (i) GRE = Point to point GRE tunnel
3.1.c (ii) Dynamic GRE = Multipoint GRE tunnel with DMVPN

[Oleg Gnedykh]

OK but next point is

3.1.d Implement and troubleshoot DMVPN [single hub]               
  3.1.d [i] NHRP
  3.1.d [ii] DMVPN with IPsec using preshared key
  3.1.d [iii] QoS profile
  3.1.d [iv] Pre-classify

So, I've finally involved. If Dynamic GRE is part of DMVPN, then why divided it in Blue Print
https://learningnetwork.cisco.com/docs/DOC-22706

[Jon Marshall]

You would have to ask Cisco that question or perhaps try the Cisco Learning Network.

Dynamic GRE to me just means you don't have to statically configure the tunnel destination IP address, it is dynamically learnt.

Although as NHRP, which is the method used to do this, is included in the next section I understand the confusion.

There is actually a separate dynamic GRE ietf draft using DHCP but I am mot aware this is what Cisco is asking about.

Like I say try CLN as they concentrate on certifications there.

Jon